Head of security at Busch Stadium Joe Walsh tells the St. Louis Post-Dispatch that Colin Grundstrom “appeared to have been drinking” Thursday night.

The admission comes as no surprise considering Grundstrom stormed the
field without wearing any clothes at the start of the seventh inning of
the Cardinals-Phillies game Thursday.
AP reports that the 22-year-old streaker who ran naked onto the field
says he did so because he lost a bet. Being on the wrong side of this
wager could end up being very costly for Grundstrom, as he has been
charged with violating two city ordinances – being a spectator running
on the playing field, and lewd and lascivious behavior. Grunstrom spent
Thursday night in jail.